As shown in the patent documents 1 and 2, a conventional four-wheel-drive vehicle is equipped, for example, with an electronically controlled driving force control device. The four-wheel-drive vehicle shown in patent documents 1 and 2 has front wheels as primary drive wheels and rear wheels as auxiliary drive wheels by controlling driving force allocated to the rear wheels by means of a driving force allocation device that is arranged between the front wheels and rear wheels. This driving force control device is equipped with a control means (FI/AT/ECU) for controlling the engine and automatic transmission and calculates total driving force of the vehicle based on FI information such as engine rotational speed, intake pipe pressure, and intake air quantity input in the FI/AT/ECU and AT information such as gear position and torque converter ratio, so as to be set to output driving torque for rear wheels appropriate to the driving mode at that time. Moreover, the driving force control device ensures driving performance on snow or rough road and protects clutch by reducing clutch slip by detecting idle running of the front wheels (or the primary drive wheels) with wheel speed sensors to perform control (or differential rotation control) such as increasing the output torque of four-wheel-drive.